1. Field of the Invention
This invention relates to a novel process for producing an open-cell foam of plasticized polyvinyl chloride having outstanding water permeability and breathability.
2. Description of Prior Art
Cellular bodies of plasticized polyvinyl chloride are usually of closed-cell structure and lack water permeability and breathability, unlike polyurethane foams.
An open-cell foam can be produced from plastisol PVC by use of "Vinyfoam AZ-F" (Ohtsuka Chemicals and Drugs Co., Ltd.)--a blowing agent specially developed for plastisol PVC or by use of azodicarbonamide and waseline or paraffin in combination. However, it has been impossible to produce open-cell foams from plastisol PVC by use of a commonly employed blowing agent such as azodicarbonamide alone.
The processing of plastisol is normally performed in the liquid phase, and the production of a foam from plastisol is carried out by a coating method which is not suitable for continuous and volume production. A process for producing open-cell foams by calendering has been in demand, however, no such process has as yet been developed.